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@ -11,38 +11,28 @@ count_energized = ->(start, dir) {
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coord, delta = current.shift
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seen << [coord, delta]
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case [elem = input[coord], delta]
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in [nil, _]
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# the beam has escaped the contraption
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in [?., _] | [?|, [_,0]] | [?-, [0,_]] # keep going
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current << [coord.zip(delta).map { _1 + _2 }, delta]
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in [?|, [0,_]] # split up and down
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current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
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current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
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in [?-, [_,0]] # split left and right
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current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
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current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
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in [?/, [0,1]] # going right, goes up
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current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
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in [?/, [0,-1]] # going left, goes down
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current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
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in [?/, [1,0]] # going down, goes left
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current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
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in [?/, [-1,0]] # going up, goes right
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current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
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in [?\\, [0,1]] # going right, goes down
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current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
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in [?\\, [0,-1]] # going left, goes up
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current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
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in [?\\, [1,0]] # going down, goes right
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current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
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in [?\\, [-1,0]] # going up, goes left
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current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
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else
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fail "unexpected element: #{elem.inspect}"
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end
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current = current.reject { seen.include?(_1) }
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next_delta = case [input[coord], delta]
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in [nil, _]
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[] # the beam has escaped the contraption
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in [?., _] | [?|, [_,0]] | [?-, [0,_]] # keep going
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[delta]
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in [?|, [0,_]] # split up and down
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[[-1,0], [1,0]]
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in [?-, [_,0]] # split left and right
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[[0,-1], [0,1]]
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in [?/, _]
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[delta.map { -_1 }.reverse]
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in [?\\, _]
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[delta.reverse]
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else
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fail
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end
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current.concat(
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next_delta
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.map {|d| [coord.zip(d).map { _1 + _2 }, d] }
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.reject { seen.include?(_1) }
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)
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end
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seen.map(&:first).select { input.has_key?(_1) }.uniq.size
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